580 
FXUS65 KVEF 140422 AAA
AFDVEF

Area Forecast Discussion
National Weather Service Las Vegas NV
822 PM PST Tue Feb 13 2018

.SYNOPSIS...A weather system lingering in the area will result in 
widespread cloudy and cool conditions through Wednesday with light
and spotty precipitation. Best chances for shower activity will 
mainly be along and east of I-15. Dry and slowly warming 
conditions are expected Thursday onward. 

&&

.UPDATE...Late afternoon light showers over Mohave County that 
drifted north into northeast Clark County have weakened according to 
radar. Latest HRRR and NAM indicate the region will be dry tonight 
as an upper low spins off the southern California coast. Low will be 
kicked inland tomorrow afternoon and evening ahead of upstream 
trough digging down the Pacific Northwest coast. Models in decent 
agreement showing isolated/scattered showers developing over parts of 
Clark, Lincoln and Mohave Counties starting late morning and lasting 
through the night, especially for eastern Lincoln and Clark Counties 
and all of Mohave County. Updated to remove POPs the rest of tonight 
and adjust sky cover based on latest satellite. 

&&

.SHORT TERM...

Some showers will continue over the area, mainly east of I-15.
Showers should decrease as the parent low pressure system
retrogrades back west off the California Coast and limits the 
amount of instability over the region. 

Wednesday will see a return to some showers across the area,
as the low begins to track back inland, hover precipitation
amounts are expected to be relatively light, and mainly over
Northwest Arizona, although some showers could make it towards 
I-15.

Additional unsettle conditions are expected on Thursday as the 
large scale trough pattern continues over the Western United 
States. Some showers are expected, however most of the activity
will be outside the area and rainfall is expected to not be
measurable. 

Temperatures over the next few days will feel seemingly cool 
compared to the past few weeks of mild weather, but will actually be 
fairly typical of mid February, hovering within a couple degrees of 
daily normals. 

&&

.LONG TERM...

Confidence is high that most of our region will see generally 
tranquil weather at least the first couple days of the holiday 
weekend. Confidence starts to diminish from Sunday onward due 
disagreement among the medium range operational models and large 
spread in ensemble members.

A dry northwest flow behind the exiting shortwave will be over our 
area Friday with some north winds likely gusting 20-30 mph along the 
Colorado River Valley from Laughlin-Bullhead City to Lake Havasu. 
Winds will decrease Saturday as zonal flow sets up in advance of a 
broad trough slowly dropping out of British Columbia into the 
Pacific Northwest. The 00Z ECMWF is the fastest at diving the base 
of this system into California and Nevada Saturday night and Sunday 
while the GFS keeps the base of the trough over the northwest states 
through early Monday. The GFS eventually digs it over our region 
late Monday into Tuesday. None of the models indicate much moisture 
being pulled our way since it maintains a more overland trajectory.
There will be limited moisture and instability with the cold pool 
leading to the potential of some snow showers over the mountains, 
but the probability of precip is quite low for now. So, if the more 
aggressive ECMWF ends up being more correct, the main effect would 
be considerably colder temperatures and gusty winds as the trough 
digs over our forecast area Sunday through Tuesday, along with 
isolated to scattered snow showers. The forecast grids are largely 
based on the blended models, but weighted a little more toward the 
ECMWF. This results in noticeably cooler temps early next week.

&&

.AVIATION...For McCarran...Ceilings between 7-9 kft are expected 
through about 23-00Z, after which scattered clouds may persist in 
the 7-9 kft layer through the evening. Cloud coverage is expected to 
decrease through the afternoon, with ceilings around 5-7 kft forming 
again just before sunrise Wednesday. Any shower activity during the 
evening is expected to remain confined to the higher terrain, mainly 
to the east. Light winds are forecast, favoring an easterly 
direction through about 03Z, then shifting to southwesterly after 
that time. Stronger southwest winds may develop after 18Z Wednesday.

For the rest of southern Nevada, northwest Arizona and southeast 
California....Generally light winds expected across the area through 
late morning Wednesday. Cloud cover will be greatest across 
northwest AZ, with less cloud coverage across eastern CA. Expect SCT 
to perhaps some BKN ceilings of 7-9 kft across NW Arizona and 
portions of southern NV through the afternoon, with improving sky 
conditions by early evening. Areas of mountain obscuration and light 
showers are possible north of KIGM and east of KLAS through the 
evening hours. Expect redevelopment of ceilings over portions of 
southern NV and northwest AZ around sunrise Wednesday, with 
increasing southwest winds after 18Z or so Wednesday.

&&

.SPOTTER INFORMATION STATEMENT...Spotters are encouraged to report
any significant weather or impacts according to standard operating 
procedures.

&&

$$

Update...Pierce

DISCUSSION...99

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